During warping, while running off the creel, each thread is commonly held by a brake, in order to put it on the beam with uniform tension. In high-speed warping mills, such braking is undesired, since the resistances at thread guides to the beam already impart sufficient tension to the thread. In addition, in high-speed warping mills, a brake would lead to too high a thread tension.
On the other hand, however, it is necessary to brake the thread moving at high speed in order to avoid continued pay-out when the warping mill has to be suddenly stopped or braked, e.g.--because of a thread fault. In such high-speed warping mills, clamping brakes have therefore been provided for each thread. These clamping brakes have been mechanically actuated (i.e., when the warping beam rotation is stopped, the clamping brakes are switched on, brought into the braking position, and are released again after the warping beam is started).
However, the mechanics of operation of such clamping brakes are very slow and, because of the large number of thread brakes on the warping mill, hard to handle. When the warping beam rotation is stopped in warping mills with a large number of threads, in particular, it is virtually impossible to switch on all thread brakes fast enough to prevent with certainty additional pay-out of threads. Similarly, when the warping mill is started, it is virtually impossible to release all the brakes before high speeds are attained, in order to prevent too high a tension on the threads.